This invention relates to still cameras having multiple frame burst capability and, more particularly, to still cameras and methods of operating still cameras wherein the number of sequential exposures per multiple frame burst is increased.
Thirty-five millimeter still cameras having the capability for fully automatic, movie-like bursts of sequential exposures have long been known. In accordance with conventional practices, bursts of sequential exposures are usually accomplished by simply speeding up the normal film-exposing functions of starting a film drive motor to transport a frame, stopping the drive, and exposing the frame. In amateur cameras, this is usually accomplished at a cyclic rate of one or two frames/second. For cameras utilized by professionals, auxiliary winders have been incorporated in order to increase the rate.
In most cameras, it is necessary to start and stop the take-up drive between exposures. For example, in U.S. Pat. No. 4,034,388, a clutch is engaged to advance a filmstrip and disengaged prior to exposing the filmstrip. As is also evident from U.S. Pat. No. 4,034,388, torque is maximized and motor size minimized by gearing down the motor output to the take-up spool and having a motor with an armature that rotates at very high speed. In some still cameras, the motor speed is reduced prior to stopping the film. Since exposures are usually in the 10 ms range, disengaging or slowing down the motor consumes at least an order of magnitude more time than exposing the film. Accordingly, there is an opportunity to increase the number of exposures per second by altering the way in which the filmstrip is started and stopped.